Gel formulations containing insecticide

ABSTRACT

The present invention relates to novel insecticidal gel formulations for the controlled and sustained release of insecticidally active compounds by means of a heat source.

The present invention relates to novel insecticidal gel formulations forthe controlled and sustained release of insecticidal active compounds bymeans of a heat source. These novel gel formulations are characterizedin that they comprise at least one type of insecticide and at least onevaporization-controlling substance (vaporization modifier), incombination with a solid suitable as a gel former.

The present invention is based on known gel formulations as described inEP 0 693 254, where insecticidally active compounds with novel,alternative solvents in combination with perfumes, colorants andauxiliaries are to display an optimum effect without decomposition for arelatively long period of time.

This novel active compound formulation is to be used in deep-drawn orcast containers made of polymer or metal, these containers being open orclosed by means of suitable fabrics, films made of polymer, for examplepolypropylene film, or metal, which are permeable to the volatilecomponents, as described in EP 0 693 254. These deep-drawn containerscan be used in an electrical heating device for killing insects, forexample mosquitoes.

In the case where mosquitoes are killed using an electrical heatingdevice, a so-called tablet vaporizer, it is generally known thatspecifically selected substances, such as cellulose board and cottonboard, asbestos, ceramics and/or porous synthetic resins are impregnatedwith pyrethroid insecticides to obtain insecticide tablets, theinsecticides being volatilized by the action of the mosquito killingheating device, which generates a temperature of 120-190° C.

A considerable disadvantage of these tablet vaporizers is theunfavourable ratio between energy input and active compound to bevaporized, since the proportion of active compound relative to theauxiliaries is to be considered as low. Furthermore, the high workingtemperature of these tablet vaporizers means that only few activecompounds are suitable for this purpose in the first place, and that,moreover, these active compounds are released over the predeterminedperiod of action in a non-uniform manner, for system reasons. The periodof action of these vaporizer tablets is limited to a maximum of 12hours. Finally, the unfavourable ratio of active compound/activecompound carrier requires a substantial, constantly available stock ofvaporizer tablets, which means that large amounts of material arenecessary as carriers and packaging material.

The devices which are already widely used for domestic purposes, inwhich a solution of an insecticidally active compound is vaporized bymeans of a heated wick (GB 2 153 227), where the active compound isdissolved in a kerosene mixture of saturated aliphatic hydrocarbonswhich is vaporized electrically by means of the wick, also haveconsiderable disadvantages.

Apart from the fact that these vapour-producing systems also operate attemperatures of between 120 and 190° C., they require a specificdistribution system (wick) and considerable amounts of solvents. Whenthe product is used, the superproportional amount of solvent relative tothe active compound results in a high concentration of solvents oradjuvants in the room, which, in turn, leads to dirtying of walls andobjects in the vicinity of these devices, which has frequently beenobserved by customers and given cause for complaint.

Other disadvantages of these formulations are the high volume of thesolvent containers and the risk of the solvent leaking, which means thatthere are substantial problems during transport and hazards in use.

Furthermore, EP 0 693 254 mentions gel formulations which have thedisadvantage that they persist for a long time indoors and that theyadditionally consist of very expensive components.

The novel insecticide-comprising gel formulations according to theinvention include mixtures which comprise at least one type of apyrethroid insecticide, a vaporization-controlling substance and aninorganic solid suitable as a gel former.

Suitable active compounds which can be used are the active compoundsmentioned in EP 0 693 254.

Particularly suitable here are formulations with the active compoundtransfluthrin (Bayothrin®, 2,3,5,6-tetrafluorobenzyl(+)-1R-trans-2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropanecarboxylate)having a reduced active compound content and in combination with novelvaporization-controlling substances, also referred to as vaporizationmodifiers, which have a strongly reduced risk potential duringprocessing and which are furthermore rapidly degradable indoors.

Preferred novel vaporization modifiers are medicinal white oils CAS No.8042-47-5 (BP Enerpar M002®) and high-pressure hydrogenated mineral oilsCAS No. 8042-47-5 (Enerpar M1930®).

Particular preference is given to naturally regrowing raw materials suchas rapeseed oil, rapeseed oil methyl ester and colourless to slightlyyellowish Guerbet alcohol of liquid/solid consistency having a very weakintrinsic odour, CAS No.: 67 187-86-0 (Guerbitol 32/36®), colourless toslightly yellowish Guerbet aalcohol of liquid consistency having veryweak intrinsic odour=2-hexyldecan-1-ol, CAS No.: 36311-34-9 (Guerbitol16®).

Particular preference is given to colourless to slightly yellowishGuerbet alcohol of liquid consistency=2-hexyldecan-1-ol, CAS No.:36311-34-9 (Guerbitol 16®).

The formulations generally comprise between 1.0 and 95% by weight ofinsecticidally active compound, preferably between 5.0 and 80%, inparticular from 20 to 50% by weight.

The formulations furthermore generally comprise between 10 and 90% byweight of vaporization modifiers, preferably between 40 and 80%, andgenerally between 1 and 12% of gel former, preferably between 6 and 10%.

The ratio of active compound/vaporization modifier in theinsecticide-comprising gel formulations according to the invention isbetween 9 and 0.1; preferably between 2.0 and 0.2.

It is furthermore possible to add organic or inorganic auxiliaries,stabilizers, perfumes and colorants, as described in EP 0 693 254, interalia, to these mixtures.

The formulations must have an optimum storage stability over a longperiod of time.

The gel formulations according to the invention are prepared by firststirring at room temperature in a suitable mixing apparatus (planetarypaddle mixer) the active compound with the vaporization modifier andstabilizer and, if appropriate, additional solvents, to give a clearsolution. Then, the gel former is added under reduced pressure, and themixture is stirred vigorously until a homogeneous gel is formed. Beforethe gel former is mixed in to give the final gel product, perfume oilsand colorants can optionally be added to the existing clear solutionwith stirring until the mixture is completely homogeneous.

For use, the film container with the coloured gel is inserted into aheating device whose front is transparent or fitted with an inspectionopening.

During the use of the heating device, the content of the film container,which is not visible through a colour marking on the container itself oron the heating device, dries out.

Only the empty film container is still visible through the transparentfront of the heating device or through the inspection opening.

A further variant for visual identification of the end point using addedcolorants may also take the form of a change in colour when the activecompounds and, if appropriate, the solvent have vaporized.

The present invention is to be illustrated by the present examples:

EXAMPLE 1

Formulations having Novel Vaporization Modifiers

Example Insecticide content Gel former Stabilizer Vaporization modifier1.1. 25% Transfluthrin ® 6% Aerosil 200 ® 1% BHT 64% Enerpar M002 ® 1.2.25% Transfluthrin ® 8% Aerosil COK 84 ® 1% BHT 64% Guerbitol 16 ®

EXAMPLE 2

The insecticide-comprising gel formulations can be prepared as follows:

2.1

For a 100 kg batch, 25 kg of liquid Transfluthrin® (temperature about40° C.) are initially charged in a stirring apparatus, 64 kg of EnerparM002® and 1 kg of BHT are added and the mixture is stirred to give aclear solution. Additionally, it is possible to stir into theformulation preferably the perfume oils aurantiol, citronella oil,C10-C16 aldehyde, birch tar oil, benzyl salicylate, lavender oil or roseoil in combination with, or without, the colorants Hostasol yellow®,Resolin-brilliant red BLS®, 1,4-diaminoanthraquinone, Alizarin VK6/225,Fatty Red HRR®, Fatty Red G®, Solvaperm Green G or Sudan Blue 670®. Withrapid stirring, 6 kg of Aerosil 200 are introduced into the clearsolution under reduced pressure until a gel has formed.

2.2

For a 100 kg batch, 25 kg of liquid Transfluthrin® (temperature) about40° C. are initially charged in a stirring apparatus, 64 kg of Guerbitol16® and 1 kg of BHT are added and the mixture is stirred to give a clearsolution. Additionally, it is possible to stir into the formulationpreferably the perfume oils aurantiol, citronella oil, C10-C16 aldehyde,birch tar oil, benzyl salicylate, lavender oil or rose oil incombination with, or without, the colorants Hostasol yellow®,Resolin-brilliant red BLS®, 1,4-diaminoanthraquinone, Alizarin VK6/225,Fatty Red HRR®, Fatty Red G®, Solvaperm Green G or Sudan Blue 670®. Withrapid stirring, 8 kg of Aerosil COK 84® are introduced into the clearsolution under reduced pressure until a gel has formed.

For use, the gel formulations are, depending on the duration of use,filled into deep-drawn or cast containers generally in amounts of0.2-0.5 g, preferably in amounts of 0.2-0.3 g, and sealed withpolypropylene film. Preferred container materials are aluminium,polyester, polyethylene, metals. The dimensions of the container arechosen such that the area of the bottom of the container has the samesize as the heating area of the heating device and transferstemperatures of from 70 to 112° C.

The controlled and sustained release of insecticidally active compoundsis effected by using Examples 2.1 and 2.2 as follows:

1.6 g of the insecticide-comprising gel formulations are uniformlydistributed on the surface of deep-drawn aluminium container having thedimensions (4×2.5×0.4 cm) and sealed with the PP film Walothen C5OSE® orTrespaphan 6ND50®. In a heating device having a temperature of 100-112°C., the container is heated for 8 hours each day, and the release ratesof the formulation are determined.

The results of the vaporization tests are shown in Example 3.

EXAMPLE 3

Release Rates of the Formulations from Example 1.1 and 1.2 in [mg/h]

Heater temperatures: 105-107° C. Voltage: 230 V Room temperature: 20-22°C. Duration of the cycle: 8 h Cycle pause: 4 h Weighed-out formulation:1.6 g

Example 1.1 Example 1.2 Cycle Weight loss per hour in mg  1 4.6 4.6  24.8 4.5  3 4.1 4.4  4 4.1 4.3  5 3.2 4.8  8 3.2 4.4 10 3.2 4.3 12 3.24.1 14 2.7 4.0 16 2.5 3.8 18 2.4 3.5 20 2.2 3.5 22 2.0 3.9 24 2.0 3.8 262.0 3.4 28 2.1 3.3 30 1.4 2.9 32 1.2 2.6 34 1.3 2.5 36 1.2 2.7 38 1.02.3 40 1.1 2.2 42 0.9 2.2 44 0.8 1.6 46 0.8 1.3 48 0.8 1.2 50 0.6 1.0

EXAMPLE 4

Biological Effect on Mosquitoes of the Variety Aedes Aegypti, Sensitive

Room size: 36 m³ Kind of room: 1 window, open temperature: 20-28° C.rel. humidity in the room: 17-34% heater temperature: 105-110° C.content of active compound: 25% of transfluthrin weighed-outformulation: 1.6 g

Duration of operation/ Formulation 1.1 Formulation 1.2 ExaminationMosquitoes KD effect after KD effect after after days released min or h% dead after min or h % dead after (hours) after hours 50% 100% 9 h 24 h50% 100% 9 h 24 h 1 day 0 1 h 03′ 1 h 15′ 100 100 1 h 14′ 2 h 02′ 100100 1 19′ 1 h 05′ 100 100 39′ 59′ 100 100 2 10′ 17′ 100 100 11′ 16′ 100100 3 4′ 7′ 100 100 32′ 45′ 100 100 4 4′ 7′ 100 100 9′ 17′ 100 100 5 4′6′ 100 100 7′ 21′ 100 100 6 3′ 5′ 100 100 12′ 22′ 100 100 7 4′ 5′ 100100 15′ 24′ 100 100 8 hours 8 4′ 5′ 100 100 7′ 18 100 100 2 days 0 53′ 1h 21′ 100 1 h 02′ 1 h 34′ 100 1 29′ 1 h 02′ 100 1 h 04′ 2 h 20′ 100 221′ 35′ 100 1 h 03′ 1 h 30′ 100 3 13′ 23′ 100 44′ 1 h 35′ 100 4 14′ 24′100 37 1 h 12′ 100 5 7′ 13′ 100 35′ 1 h 14′ 100 6 9′ 20′ 100 23′ 40′ 1007 7′ 13′ 100 26′ 45′ 100 16 hours 8 5′ 8′ 100 9′ 14′ 100 7 days 0 41′52′ 100 100 1 h 10′ 1 h 34′ 100 100 1 24′ 42′ 100 100 39′ 1 h 24′ 100100 2 8′ 14′ 100 100 34′ 1 h 03′ 100 100 3 8′ 16′ 100 100 15′ 54′ 100100 4 7′ 15′ 100 100 18′ 30′ 100 100 5 8′ 17′ 100 100 24′ 41′ 100 100 68′ 16′ 100 100 19′ 31′ 100 100 7 7′ 14′ 100 100 16′ 44′ 100 100 56 hours8 6′ 11′ 100 100 7′ 12′ 100 100 13 days 0 30′ 43′ 100 100 29′ 48′ 100100 1 6′ 11′ 100 100 8′ 13′ 100 100 2 4′ 8′ 100 100 6′ 10′ 100 100 3 3′4′ 100 100 4′ 9′ 100 100 4 2′ 5′ 100 100 4′ 8′ 100 100 5 3′ 6′ 100 1007′ 22′ 100 100 6 2′ 6′ 100 100 6′ 12′ 100 100 7 2′ 7′ 100 100 5′ 8′ 100100 104 hours 8 2′ 6′ 100 100 5′ 8′ 100 100 20 days 0 42′ 57′ 100 10038′ 55′ 100 100 1 5′ 11′ 100 100 3′ 7′ 100 100 2 5′ 11′ 100 100 2′ 6′100 100 3 4′ 8′ 100 100 2′ 4′ 100 100 4 5′ 7′ 100 100 2′ 4′ 100 100 5 6′9′ 100 100 2′ 6′ 100 100 6 5′ 8′ 100 100 2′ 5′ 100 100 7 4′ 8′ 100 1002′ 7′ 100 100 160 hours 8 5′ 7′ 100 100 2′ 6′ 100 100 27 days 0 1 h 28′1 h 53′ 100 100 42′ 52′ 100 100 1 1 h 13′ 2 h 05′ 100 100 35′ 49′ 100100 2 1 h 01′ 1 h 35′ 100 100 10′ 50′ 100 100 3 40′ 1 h 13′ 100 100 7′14′ 100 100 4 23′ 43′ 100 100 7′ 12′ 100 100 5 33′ 53′ 100 100 8′ 15′100 100 6 8′ 18′ 100 100 4′ 8′ 100 100 7 20′ 58′ 100 100 3′ 5′ 100 100216 hours 8 7′ 11′ 100 100 3′ 5′ 100 100 35 days 0 1 h 25′ 2 h 20′ 100100 1 h 00′ 1 h 13′ 100 100 1 43′ 1 h 15′ 100 100 11′ 43′ 100 100 2 28′1 h 03′ 100 100 5′ 10′ 100 100 3 43′ 1 h 03′ 100 100 3′ 7′ 100 100 4 13′1 h 18′ 100 100 3′ 7′ 100 100 5 15′ 58′ 100 100 2′ 7′ 100 100 6 20′ 1 h05′ 100 100 3′ 18′ 100 100 7 8′ 28′ 100 100 2′ 9′ 100 100 280 hours 810′ 48′ 100 100 2′ 7′ 100 100 42 days 0 2 h 23′ 3 h 05′ 100 100 53′ 1 h28′ 100 100 1 2 h 43′ 3 h 15′ 100 100 1 h 05′ 1 h 45′ 100 100 2 1 h 43′2 h 48′ 100 100 53′ 1 h 35′ 100 100 3 1 h 53′ 3 h 50′ 100 100 1 h 00′ 1h 55′ 100 100 4 1 h 20′ 2 h 28′ 100 100 48′ 1 h 25′ 100 100 5 45′ >4 h98 100 33′ 48′ 100 100 6 38′ 1 h 28′ 100 100 12′ 55′ 100 100 7 48′ >2 h90 100 14′ 48′ 100 100 336 hours 8 >1 h >1 h 45 100 6′ 10′ 100 100 48days 0 1 h 42′ 2 h 40′ 100 1 h 40′ 2 h 20′ 100 1 2 h 45′ 3 h 50′ 100 1 h30′ 2 h 15′ 100 2 1 h 43′ 2 h 55′ 100 1 h 00′ 2 h 18′ 100 3 1 h 45′ 2 h48′ 100 1 h 03′ 2 h 05′ 100 4 1 h 23′ 2 h 13′ 100 53′ 1 h 48′ 100 5 1 h48′ >4 h 95 40′ 1 h 45′ 100 6 1 h 20′ >3 h 88 35′ 1 h 00′ 100 7 39′ >2 h90 9′ 48′ 100 384 hours 8 >1 h >1 h 60 8′ >1 h 90

Based on the present results, the biological activity of theformulations mentioned here is sufficient.

What is claimed is:
 1. A gel formulation useful in the controlled andsustained release of a vapor containing at least one insecticidallyactive compound comprising: (a) from about 1.0% to about 95% by weightof at least one pyrethroid; (b) from about 1% by weight to about 12% byweight of a gel former; and (c) from about 10% by weight to about 90% byweight of a vaporization modifier selected from the group consisting ofmedicinal white oils and high-pressure hydrogenated mineral oils havingCAS No. 8042-47-5, rapeseed oil, rapeseed oil methyl ester, Guerbetalcohols and combinations and mixtures thereof, wherein saidvaporization modifier is present in an amount sufficient to modify thevaporization rate of said gel formulation at an operating temperaturefrom about 70° C. to about 110° C.; and wherein said gel formulationforms said vapor containing at least one pyrethroid upon heating to saidoperating temperature, whereby surfaces exposed to said vapor remainsubstantially free of residues of said vaporization modifier during useof said gel formulation.
 2. The gel formulation of claim 1, wherein saidvaporization modifier is selected from the group consisting of Guerbetalcohols having CAS No. 67187-86-0or CAS No. 36311-34-9, andcombinations and mixtures thereof.
 3. The gel formulation of claim 1,wherein said pyrethroid is prallethrin.
 4. The gel formulation of claim1, wherein said pyrethrin is 3-allyl-2-methyleyelopent-2-en-4-on-1-ylD-cis/trans-chrysanthemate.
 5. The gel formulation of claim 1, whereinsaid pyrethrin is 1-ethinyl-2-methyl-2-pentenyl 2,2dimethyl-3-(2-methyl-1-propenyl)-cyclopropane-carboxylate.
 6. The gelformulation of claim 1, wherein said at least one insecticidally activecompound comprises a natural pyrethrum.
 7. The gel formulation of claim1, wherein said pyrethroid comprises from about 5.0% to about 80% byweight of said gel formulation.
 8. The gel formulation of claim 7,wherein said pyrethroid comprises from about 20% to about 50% by weightof said gel formulation.
 9. The gel formulation of claim 1, wherein saidvaporization modifier comprises from about 40% by weight to about 80% byweight of the formulation.
 10. The gel formulation of claim 1, whereinsaid gel former comprises from about 6% by weight to about 10% by weightof the formulation.
 11. The gel formulation of claim 1, wherein theratio of the total weight of said pyrethroid in said gel formulation tothe total weight of said vaporization modifiers is from about 9 to about0.1.
 12. The gel formulation of claim 11, wherein said ratio is fromabout 2.0 to 0.2.
 13. The gel formulation of claim 1, wherein saidpyrethroid comprises transfluthrin.
 14. The gel formulation of claim 1further comprising a container for holding said gel formulation duringheating to a temperature from about 70° C. to about 110° C.
 15. The gelformulation of claim 14, further comprising a heating device adapted toheat said gel formulation in said container to said temperature.